Targeting disease-causing gene sequences was first suggested nearly 40 years ago (Belikova et al., Tet. Lett., 1967, 37, 3557-3562), and antisense activity was demonstrated in cell culture a decade later (Zamecnik et al., Proc. Natl. Acad. Sci. U.S.A., 1978, 75, 280-284). One advantage of antisense technology in the treatment of a disease or condition that stems from a disease-causing gene is that it is a direct genetic approach that has the ability to modulate expression of specific disease-causing genes.
Generally, the principle behind antisense technology is that an antisense compound hybridizes to a target nucleic acid and effects modulation of gene expression activity or function, such as transcription, translation or splicing. The modulation of gene expression can be achieved by, for example, target degradation or occupancy-based inhibition. An example of modulation of RNA target function by degradation is RNase H-based degradation of the target RNA upon hybridization with a DNA-like antisense compound. Another example of modulation of gene expression by target degradation is RNA interference (RNAi). RNAi is a form of antisense-mediated gene silencing involving the introduction of dsRNA leading to the sequence-specific reduction of targeted endogenous mRNA levels. Sequence-specificity makes antisense compounds extremely attractive as tools for target validation and gene functionalization, as well as research tools for identifying and characterizing nucleases and as therapeutics to selectively modulate the expression of genes involved in the pathogenesis of any one of a variety of diseases.
Antisense technology is an effective means for reducing the expression of one or more specific gene products and can therefore prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications. Chemically modified nucleosides are routinely used for incorporation into antisense compounds to enhance one or more properties, such as nuclease resistance, pharmacokinetics or affinity for a target RNA.
Despite the expansion of knowledge since the discovery of antisense technology, there remains an unmet need for antisense compounds with greater efficacy, reduced toxicity and lower cost. Until the present disclosure, high-affinity modifications have not been employed in the design of short antisense compounds for reducing target RNA in vivo. This is because of concerns regarding the degree of target specificity that a sequence 15 nucleotides or shorter would have when employed to reduce target in a living system. Previous studies have described that greater specificity, and therefore greater potential for potency, is achieved by antisense compounds between 16 and 20 nucleobases in length.
The present disclosure describes incorporation of chemically-modified high-affinity nucleotides into antisense compounds allows for short antisense compounds about 8-16 nucleobases in length useful in the reduction of target RNAs in animals with increased potency and improved therapeutic index. Thus, provided herein are short antisense compounds comprising high-affinity nucleotide modifications useful for reducing a target RNA in vivo. Such short antisense compounds are effective at lower doses than previously described antisense compounds, allowing for a reduction in toxicity and cost of treatment.